Hello Soyuz,
Kalman filtering is just an estimation technique. What's more important, is what you are estimating. In most cases it is the state of a mathematical model representing the aircraft kinetics. You have sensors but they are (1) too slow or (2) can have a lof of noise/drift. With a kalman filter you can "fuse" them.
Difficult things to estimate are: centripetal accelerations, accelerations on any of the 3 axis.
You can find more information on my blog (i still need to cover a lot of topics ;-) )
http://tom.pycke.be/mav/71/kalman-filtering-of-imu-data
Tom

Hello,
Does anybody know more/has anybody used this new GPS module:
https://www.futurehobbies.com/items_detail....26&item=162
Seems to be based on the MTK chipset...
I need a new GPS because I'm currently using an EB-85A with the old &bad firmware. Maybe i'll buy this one instead of the EB-85A, but the antenna looks so small!
Tom

Hello Loopforever,
Right now I'm not quite sure what I'm going to do with all this... Release it as an open-source project? Try to commercialize it? Both? :-)
But in the mean time I'll be happy to help you out with any questions or issues you might have!
I just added another feature. When making sharp turns with a roll angle of like 35 degrees or more, the plane lost altitude. An aeronautics friend of mine explained me a simplified formula to tackle this:
The lost left because of the roll angle is proportional with 1/cos(roll). Some simple vector calculus shows that. Right!
The lift of a delta/wing is more or less linear with its elevator angle RELATIVE TO THE ZERO-LIFT POSITION. That zero lift position is the down-elevator position where the plane has no lift anymore. For my plane this is around -9° .
So (pseudo code, i'm still testing it :-) ):
elevator_out = (elevator_out + 9°) /cos(roll_angle)
Tom

Hello,
I've been working no my autopilot for a while. The idea is to create a unit that serves as stabilization (with thermophiles) and servo-controller. Input for this unit is the roll and pitch angle (right now using rc-transmitter). Input could also come from uart, so a wireless digital transmitter or another microcontroller (with gps connected) can steer it.
The whole thing runs on a PIC16F877 and was packed into only 2k code :-)
More information, photos and movies on my website: http://tom.pycke.be
Comments and suggestion appreciated!

After a while I figured out that software UART was not really an option. So I tried to come up with another solution
(could be trivial for electronics experts, but i'm just a newbee ;-) )
I used a 7407. This chip is a TLL chip that implements the function IN = OUT. Logical high on the in can be as low as 2V. The out is an open-collector port. This means it needs a pull up resistor, but you can take it to any voltage level you want.
So the GPS output (2.8V logical high) goes to the 7407 input and the corresponding output has a pull-up resistor to 5V.
The PIC UART output (5V logical high) goes to the 7407, and the corresponding output goes to a 2.8 voltage reference that was created using a voltage divider (2 resistors) connected between the ground and 5V.
I hope some people found my quest usefull :-)

I was able to connect my EB-85 to my PIC!
Howto:
The standard UART port on my PIC (16F877) are ST (smidt-trigger), which only see a logical high at like 4V. Some other ports (like RB) are TLL, which see a logical high at around 2V. So the solution is to use software UART on a TTL pin.
This works perfectly.
The TX side can easily be done with 2 diodes or a voltage divider (2 resistors)
Tom

I once was unfortunate enough to get lost as well and see on camera that my plane didnt really repond anymore to my controls :-) Video was still clear tho
I lost control like 100 meters before crashing (due to low altitude?) at a distance of 1250 meters. But i often fly without any problems at 1000 meter range with fpv! But yes, further I start noticing glitches, so system that goes further would be welcome...
Maybe the aerocomm digital links would be good enough, and also servo as digital modem for gps data :-)
In Belgium we can use 433-434 upto 10mW, so I guess that's not powerfull enough to get a longer range?
TOm

Last week I did a test with the 10mW from rc-tech. I used the rc-cam patch antenna on the receiver side.
Most of the time I flew about 900 meters far, but unfortunately i was too enthousiast, and i was going further and further... Until my motor-batteries ran out! A bit paniced, I was disoriented and started flying in the wrong direction. Then I had too much noise on the controls of my plane (with an ACT digital dual conversion receiver), however, the image still remained perfect without any noise, and i could see my plane crash into a potato field. After an hour of searching I found my plane about 1250 meters from the starting site.
Thumbs up for thomas: your patch antenna performed a lot better than the rc-tech patch that came with the camera setup (i think it had a wrong polarisation).
The rc-tech transmitter and receiver are brilliant! With the stock antennas they go about 500 meters with some occasional noise, but with a good patch (and a good person pointing it ;-) ) I could go to the limits of my rc-transmitter without any signs of noise.
Does the receiver have some special sensitivity compared to other receivers?